While it is possible to use an ordinary compressor for tightening up and adding punch to a stereo mix, it is very common that low frequencies can cause "pumping" effects on the overall signal. However, by splitting the signal into 4 different frequency bands, each frequency region can be separately processed. This is achieved on the QuadComp using a series of crossover filters. These filters are constructed as linear phase FIR filters in order to produce a signal path which is perfectly free of phase errors.

Good Points
You can set the crossover frequencies for the 4 bands. Each band has controls for Threshold, Ratio, Attack and Release.